Adjustable height scaffold

ABSTRACT

An adjustable height scaffold includes an upright and a cage for mounting a work platform on the upright. The cage has two spaced side plates on opposite sides of the upright. Two crossbars are connected to the side plates for relative movement of the crossbars between a captured position with the crossbars spaced by a distance greater than the cross section of the upright and a release position spaced by a distance less than the cross section of the upright. The couplings joining the crossbars to the side plates prevent disconnection of the crossbars from the side plates in the captured position but allow disconnection of at least one of the crossbars from the side plates in the release position. With the upright in the cage between the crossbars, the crossbars cannot move to the release position. To allow the cage to be conveniently assembled on and disassembled from the upright, while the upright remains in a vertical orientation, the upright has at least a section of reduced cross section, allowing the crossbars to move to the release position for assembly or disassembly. The reduced cross section may be provided by a notch in the upright.

FIELD OF THE INVENTION

[0001] The present invention relates generally to scaffolds and more particularly to scaffolds which mount on uprights so as to be adjustable in height.

BACKGROUND

[0002] Known adjustable height scaffolds have four main parts: an upright or pole; a bracket assembly for supporting a work platform on the upright; a jack or block and tackle for raising and lowering the bracket assembly on the upright; and an upright support for supporting the upright at its top. The adjustable elements of the scaffold are the bracket assembly, the jack and the upright support which can be positioned at various heights along the upright.

[0003] Two adjustable height scaffolds for use on rectangular poles of wood or aluminium are known and used. The patent literature describing these scaffolds includes U.S. Pat. No. 2,216,912 to Hoitsma, which discloses a bracket assembly to which a jack is coupled. In U.S. Pat. No. 2,244,374 to Riblet there is disclosed an upright support which is used in combination with the bracket assembly disclosed in U.S. Pat. No. 2,342,427 to Riblet, which is raised and lowered by block and tackle. U.S. Pat. No. 3,970,277 to Riblet shows a jack coupled to a bracket assembly. The disclosures of these prior patents are incorporated herein by reference. These prior adjustable height scaffolds require the capture of the upright in a manner which permits the motion of the adjustable elements up and down the upright when not loaded but restrains these elements from motion when loaded. The known scaffolds use cages to accomplish this capture. A cage includes bolts, bars, plates or the like, hereinafter referred to as crossbars, which extend across opposite load bearing sides of the upright supports. The crossbars are mounted in side members attached, in turn, to load-bearing members that support the elements. The forces required to raise and lower the elements and support them in their fixed positions are transmitted by the load-bearing members to the side members of the cages and thence to those crossbars which bear on the upright.

[0004] The crossbars are captured in two dimensions by apertures in the side members through which they are inserted and in the third dimension by retainers, for example bolts, cotter pins, welds or clips. These retainers do not contribute to the functioning of the elements of the adjustable height scaffolds, but add to the cost of their fabrication, add to their weight and, in many cases, because of external sharp edges and protuberances, increase the risk of injury while the adjustable height scaffolds, of which they are a part, are being handled.

[0005] The present invention aims at the provision of certain improvements in adjustable height scaffolds.

SUMMARY

[0006] According to one aspect of the present invention there is provided, for use in an adjustable height scaffold having an upright with opposite inner and outer sides and a predetermined cross sectional dimension therebetween, a cage for mounting a work platform on the upright, the cage comprising:

[0007] two spaced apart side members for receiving the upright therebetween;

[0008] an inner crossbar and an outer crossbar;

[0009] crossbar couplings for connecting each of the crossbars to the two side members for relative movement of the crossbars between a captured position with the crossbars spaced by a distance greater than the predetermined cross sectional dimension between the inner and outer sides of the upright and a release position spaced by a distance less than the predetermined cross sectional dimension between the inner and outer sides of the upright, the couplings preventing disconnection of the crossbars from the side members in the captured position and allowing disconnection of at least one of the crossbars from the side members in the release position.

[0010] With the upright in the cage between the crossbars, the crossbars cannot move to the release position. To allow the cage to be conveniently assembled on and disassembled from the upright, while the upright remains in a vertical orientation, the upright may have at least a section of reduced cross section, allowing the crossbars to move to the release position for assembly or disassembly. The reduced cross section may be provided by a notch in the upright. This allows the elements of a adjustable height scaffold to be removed from the upright while it is standing vertically on a supporting surface.

[0011] The crossbar couplings may include keyhole openings in the side members, accommodating at least one of the cross bars. A crossbar engaged in the keyhole openings may have grooves, flanges or other surface irregularities providing slots or shoulders for engaging the side members at the narrow ends of the keyholes so as to retain the crossbar in engagement with the side members, while allowing the crossbar to be withdrawn endwise from the larger ends of the keyhole openings.

[0012] With this arrangement the crossbars do not require additional material or parts to fix them in place. The crossbars can be installed in the side members of the cages without special tools. The crossbars cannot be removed from the cages inadvertently.

[0013] In a simple embodiment of the invention, one of the crossbars is fixed in, or a part of, the side members of its cage. There are two matching keyholes in the respective side members of the cage. The keyholes are so dimensioned that a movable crossbar can be inserted through the larger ends thereof. The keyholes are spaced from the fixed crossbar sufficiently that the movable crossbar, when moved sufficiently into the narrow ends of the keyholes, will permit the insertion of the upright between the fixed and movable crossbars. The upright will prevent the movable crossbar from moving to the larger ends of the keyholes so that the movable crossbar can not be removed from its cage while the upright is captured therein.

[0014] For use on uprights where the force on the upright required to prevent slipping may be sufficient to mar or gall the upright, rounded jaw inserts made of a greater diameter or of a different material can be used to contact the upright. Metal or plastic uprights, for example, may be susceptible to this kind of damage. In this case, the crossbar does not directly contact the upright but instead transfers the force provided by the side members to the rounded jaw insert which contacts the upright directly. In embodiments of this type, at least one notch may be placed in the crossbar to limit the lateral motion that it can have relative to the jaw insert which it contacts.

[0015] In embodiments of this type, the lateral motion of the jaw insert with respect to the side members can be limited by small bosses at the ends of the jaw insert. This may also restrict the lateral motion of the crossbar. Since the jaw insert can be held in contact with the crossbar by the upright, the crossbar can be fixed in two dimensions by apertures, as simple as square holes, in the side members, through which they may be inserted or removed when the upright is not in place and the jaw insert has been removed from the notched crossbar.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the accompanying drawings, which illustrate exemplary embodiments of the invention:

[0017]FIG. 1 is a side view of a scaffold according to the present invention;

[0018]FIG. 2 is a side view of a first embodiment of a cage of a load activated lock;

[0019]FIG. 3 is a side view of a crossbar;

[0020]FIG. 3a is an end view of the crossbar of FIG. 3;

[0021]FIG. 4 is an elevation of an alternative embodiment of a crossbar;

[0022]FIG. 4a is an end view of the crossbar of FIG. 4;

[0023]FIG. 5 is an elevation of another alternative embodiment of a crossbar;

[0024]FIG. 5a is an end view of the crossbar of FIG. 5;

[0025]FIG. 5b is across section along line b-b of FIG. 5;

[0026]FIG. 6 is a side view of an alternative embodiment of the cage which serves as the lock for the bracket assembly;

[0027]FIG. 7 is a rear elevation of a jaw for use with a crossbar;

[0028]FIG. 7a is an end view of the jaw of FIG. 7;

[0029]FIG. 8 is a plan view of a crossbar for use with the jaw of FIGS. 7 and 7a;

[0030]FIG. 8a is an end view of the crossbar of FIG. 8;

[0031]FIG. 9 is rear elevation of an alternative embodiment of a jaw for use with a crossbar;

[0032]FIG. 9a is an end view of the jaw of FIG. 9;

[0033]FIG. 10 is a plan view of a crossbar for use with the jaw of FIGS. 9 and 9a; and

[0034]FIG. 10a is an end view of the crossbar of FIG. 10;

DETAILED DESCRIPTION

[0035] Referring now to FIG. 1, there is shown a side view of an embodiment of an adjustable height scaffold 10 with three elements mounted on an upright 12 of design width 14. A notch 16 is formed on an outer side of the upright, which leaves a section of the upright with a reduced width 18. The upright 12 represents any suitable elongate load bearing structure, for example a beam or pole. It is constructed of a suitable material, for example wood, plastic or metal. The three elements mounted on the upright are a bracket assembly 20, a jack 22 and an upright support 24.

[0036] The bracket assembly 20 includes an angle bracket 26, a lower bracket arm 28 and a lock 30. The lower bracket arm 28 is a cage which captures the upright 12 in two dimensions. It is connected to the lower end of the angle bracket by a cross rod 32. The lower bracket arm has transversely aligned keyhole apertures 34 on a side of the upright opposite the cross rod 32. The narrow ends 36 of the apertures extend beyond the outer side of the upright while the larger ends 38 overlap the upright. A crossbar 40 is engaged in the keyhole apertures to capture the upright in the lower bracket arm.

[0037] The lock 30 is also a cage that captures upright 12 in two dimensions, but is referred to as a lock because, under certain conditions, it prevents downward movement, in the third dimension, of the bracket assembly 20 on upright 12. Lock 30 includes two side members in the form of plates 42 which are pivotally attached to the angle bracket 26 by a transverse fulcrum rod 44. Each of the side plates 42 has outer and inner apertures 46 and 48 respectively. The inner aperture is a keyhole with a narrow end 50 projecting inwardly from the inner side of the upright and a large end 52 overlapping the upright. Inner crossbar 54 can be inserted in the apertures 48 when the large ends 52 of the inner apertures are unobstructed by the upright, for example with the lock at the position of the notch 16. The crossbar 54 is prevented from accidental removal when the upright 12 is captured by the lock 30. Lock 30 is load activated when mounted on an upright of design width, since the inner end 50 of inner aperture 48 lies below the plane defined by fulcrum rod 44 and the outer aperture 46.

[0038] The jack 22 includes a connector link 58 pinned to each side plate 42, a pedal 60 pinned to the connector links and a lock 62. The lock 62, also a cage, includes side members 64 which are pivotally attached at their inner ends to pedal 60 by pins 66. Each side member 64 has an inner keyhole aperture 68 with an inner narrow end 70 and an outer large end 72. Each side member also has an outer aperture 74. The outer aperture has an L-shape, including a slot section 76 extending along the side member beyond the upright and a second slot section 78 extending from the inner end of slot section 76 to the edge of the side member at a position overlapping the upright. Crossbars, not shown, can be inserted into the apertures 68 and 74 when the lock does not capture the upright 12, but can not be removed when the lock captures the upright.

[0039] The upright support 24 includes stays 80 fastened to a cage 82. The cage includes side members 84 and two fixed inner crossbars 86 connecting the side members and engaging the inner side of the upright 12. Each side member has a pair of outer keyhole apertures 88 into which removable crossbars 90 can be inserted when the upright is not captured by the cage. The crossbars 90 can not be removed when the upright is captured by said cage.

[0040] For insertion and removal of a removable cross bar from its respective cage, the cage may be moved to the position of a notch, if available. The notch 16 is deep enough to expose the large end of the keyhole aperture of the second slot section 78. From that position, the crossbar can be removed through the second slot section 78.

[0041] Referring to FIG. 2, there is illustrated an alternative form of lock cage 92. This cage has two side plates 94, each with an inner L-shaped aperture 96 with an inner end slot section 98 and a second slot section 100 leading to the edge of the side plate. Each of the side plates also has an outer keyhole aperture 102 with an outer narrow end 104 and an inner, square, large end 106. The inner apertures accommodate a crossbar 108 illustrated in FIGS. 3 and 3a, while the outer apertures accommodate a crossbar 110, illustrated in FIGS. 5, 5a and 5 b. A fulcrum rod aperture 112 is formed in each side plate 94.

[0042] Lock cage 92 is a load activated lock since inner crossbar 108 lies below the plane through outer crossbar 110 and fulcrum rod aperture 112, so a horizontal force on the fulcrum rod will create a moment forcing the two crossbars against an upright of design width.

[0043]FIGS. 3 and 3a are side and ends view of the removable inner crossbar 108. The crossbar has circumferential grooves 114 adjacent its opposite ends. Each groove provides opposed shoulders 116 and 118 for engaging opposite sides of a respective side plate 94 to prevent endwise movement of the crossbar out of the apertures 96. It is to be understood that only two opposing shoulders of the four shoulders 116 and 118 are needed to prevent the removal of the crossbar from the cage when the upright 12 is captured. For example, one groove 114 can alone prevent the removal of the crossbar when the upright 12 is present.

[0044]FIGS. 4 and 4a are side and end views of an alternative embodiment of the inner crossbar. The crossbar 122 has a set of four end flanges 124 at each end and four additional flanges 126 spaced along the crossbar to provide slots 128 between the flanges 124 and 126. The shoulders of slots 128 engage the side plates 94 in the same way as the shoulders of grooves 114 of the crossbar 108.

[0045]FIGS. 5, 5a and 5 b illustrate the crossbar 110. This crossbar has a rounded side 130 for abutting the side of the upright. The opposite side 132 is flat. The ends of the crossbar are rectangular flanges 134. Between the flanges 134 and the main body of the crossbar are U-shaped grooves 136 which accommodate the side plates 94. The end flanges 134 will pass through the larger square ends 106 of keyhole apertures 102.

[0046]FIG. 6 illustrates another embodiment of lock cage 138. Each of the two side plates has an inner keyhole aperture 140 with an inner narrow end 142 and a square, large outer end 144. Each of the side plates also has an outer square aperture 146. The inner apertures accommodate a crossbar 148 illustrated in FIGS. 8 and 8a, while the outer apertures accommodate a crossbar 150, illustrated in FIGS. 10 and 10a. A fulcrum rod aperture 152 is formed in each side plate.

[0047] The crossbar 148 has a square cross section with circular grooves 154 adjacent the ends for engaging the side plates. The centre part 156 of the crossbar has a rectangular notch 158 extending along one side. This notch accommodates a jaw 160 illustrated in FIGS. 7 and 7a. The jaw is a cylindrical section block with a rounded face 162 to engage the side of the upright and a groove 164 along the side of the block opposite the face 162 to engage over the centre part 156 of the crossbar. This crossbar may be released from the cage, when it does not capture the upright by removing the jaw and then moving the crossbar to the large end of the aperture 140 for endwise removal of the crossbar.

[0048]FIGS. 10 and 10a illustrate a crossbar 150 with a square body 166 with a long, flat recess 168 along one side. The crossbar slides endwise into the square aperture 146 in the cage side plates. FIGS. 9 and 9a illustrate cylindrical section jaw 170 with a rounded face 172 for abutting the upright. Along the side opposite face 172, the jaw has a groove 174 which fits over recess 168 in the notched crossbar 150 so that the crossbar is restrained from moving along the jaw. The jaw has short, partial sleeves 176 at its opposite ends to engage the inner surfaces of side members 138. The jaw acts as a retainer to hold the crossbar in place in the cage. To release the crossbar, the cage is moved to the reduced cross section part of the upright or removed from the upright entirely and the jaw is separated, allowing the crossbar to be withdrawn endwise.

[0049] While particular embodiments of the present invention have been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention and are intended to be included herein. For example, the crossbars shown in FIGS. 3, 4, 5, 8 and 9 as linear may be curved in length to contact the inner and outer surfaces of a pole or upright having a circular rather than a rectangular cross section. Moreover, neither the particular nature of the apertures 38, 46, 72, 74 and 88 in the side members not the opposing shoulders, provided by irregularities 114, 128, 136, 154 and 168 in the crossbars in the cages of an adjustable height element constitute the novelty of these cages.

[0050] The novelty of a cage depends entirely on the location of specially shaped apertures in the side members of the cage so that a crossbar, provided with sufficient irregularities, can be removed from the cage when and only when the cage does not capture an upright of design dimensions.

[0051] In view of the various modifications that can be made within the scope of the present invention, the invention is to be limited solely by the scope of the appended claims. 

Embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A cage for use in an adjustable height scaffold having an upright with opposite inner and outer sides and a predetermined cross sectional dimension therebetween, the cage comprising: two spaced apart side members for receiving the upright therebetween; an inner crossbar and an outer crossbar; crossbar couplings for connecting each of the crossbars to the two side members for relative movement of the crossbars between a captured position with the crossbars spaced by a distance greater than the predetermined cross sectional dimension between the inner and outer sides of the upright and a release position spaced by a distance less than the predetermined cross sectional dimension between the inner and outer sides of the upright, the couplings preventing disconnection of the crossbars from the side plates in the captured position and allowing disconnection of at least one of the crossbars from the side members in the release position.
 2. A cage according to claim 1 wherein the crossbar couplings include keyhole openings in the side members, accommodating at least one of the crossbars.
 3. A cage according to claim 2, said at least one of the crossbars having a transverse cross section smaller than larger ends of the keyhole openings whereby said at least one of the crossbars may be removed endwise from the key hole openings.
 4. A cage according to claim 2 wherein said at least one of the crossbars comprises grooves for engaging the side plates at the narrow ends of the keyholes so as to retain the crossbar in engagement with the side members.
 5. A cage according to claim 2 wherein said at least one of the crossbars comprises flanges for engaging the side plates at the narrow ends of the keyholes so as to retain the crossbar in engagement with the side members.
 6. A cage according to claim 1 wherein one of the crossbars is secured to the side members of the cage.
 7. A cage according to claim 1 including rouinded jaws mounted on respective ones of the crossbars to contact the upright.
 8. A cage according to claim 7 including at least one notch in each crossbar for receiving the respective jaw to limit motion of the respective jaw along the crossbar.
 9. A cage according to claims 7 including bosses at the ends of each rounded jaw for engaging the respective side members.
 10. A cage according to claim 1 including rounded jaws mounted on respective ones of the crossbars to contact the upright and wherein the crossbar couplings include openings in the side members, the openings having a cross sectional configuration larger than at least one of the crossbars and smaller than a combined cross sectional configuration of the crossbar and jaw.
 11. An adjustable height scaffold comprising: an upright with opposite inner and outer sides with a predetermined cross sectional dimension therebetween, and at least a section of said upright having a reduced cross sectional dimension smaller than said predetermined cross sectional dimension; and a cage for mounting on the upright, the cage comprising: two spaced apart side members for receiving the upright therebetween; an inner crossbar and an outer crossbar for engaging the inner and outer sides respectively of the upright; crossbar couplings for connecting each of the crossbars to the two side members for relative movement of the crossbars between a captured position with the crossbars spaced by a distance greater than the predetermined cross sectional dimension between the inner and outer sides of the upright and a release position spaced by a distance between said reduced cross sectional dimension and said predetermined cross sectional dimension, the couplings preventing disconnection of the crossbars from the side members in the captured position and allowing disconnection of at least one of the crossbars from the side members in the release position.
 12. A scaffold according to claim 11 wherein the section of the upright comprises a notch in the upright.
 13. A cage according to claim 11 wherein the crossbar couplings include keyhole openings in the side members, accommodating at least one of the crossbars.
 14. A cage according to claim 13, said at least one of the crossbars having a transverse cross section smaller than larger ends of the keyhole openings whereby said at least one of the crossbars may be removed endwise from the key hole openings.
 15. A cage according to claim 13 wherein said at least one of the crossbars comprises grooves for engaging the side plates at the narrow ends of the keyholes so as to retain the crossbar in engagement with the side members.
 16. A cage according to claim 13 wherein said at least one of the crossbars comprises flanges for engaging the side members at the narrow ends of the keyholes so as to retain the crossbar in engagement with the side members.
 17. A cage according to claim 11 wherein one of the crossbars is secured to the side members of the cage.
 18. A cage according to claim 11 including planar jaws mounted on respective ones of the crossbars to contact the upright.
 19. A cage according to claim 18 including at least one notch in each crossbar for receiving the respective jaw to limit motion of the respective jaw along the crossbar.
 20. A cage according to claims 18 including bosses at the ends of each planar jaw for engaging the respective side members.
 21. A cage according to claim 11 including planar jaws mounted on respective ones of the crossbars to contact the upright and wherein the crossbar couplings include openings in the side members, the openings having a cross sectional configuration larger than at least one of the cross bars and smaller than a combined cross sectional configuration of the crossbar and jaw. 